In the production of glass containers by the press and blow method on the well known I. S. type machine, a gob of glass is provided to a blank or parison mold comprising two mold members or halves. These mold halves are supported by opposed arms of a mold open and close mechanism at a blank station of the machine, which mold members can be closed to form a mold cavity. The glass in the mold cavity is pressed into the required shape of a parison by a plunger moving upwardly into the mold cavity, a lower portion of the glass being forced into a neck ring of the mold. The plunger is then withdrawn and the parison is carried by the neck ring away from the blank station and is transferred to a blow mold station where it is blown to the required shape. In the blow and blow method a gob of glass is provided to the parison mold and is then blown into the required shape of a parison. The shaped parison is again carried by a neckring away from the blank station to a blow mold station.
It will be understood that the mold members must be accurately located, i.e., there must be a datum from which their position is located with respect to other parts of the machine, particularly the plunger mechanism and the neck ring mechanism. Customarily each mold arm is made up of upper and lower hanger members and the mold halves include downwardly depending hooks which hang on these members with the location of the horizontal surface where the hook is supported defining the datum for the mold. Normally the hooks are located at the top of the mold half but GB 2175296 shows a variant construction in which the mold member has its vertical position determined by a lower hanger member.
Accurate location of the mold members is of course also required when one set of mold members is exchanged for another set of different size. Conventionally this is done by substituting the hanger members used with one set of molds by hanger members appropriate for the new set of molds. Such hanger members are fairly expensive, and what is more, if the mold arms are optimally positioned to close the molds with pressure applied to upper and lower end portions of the mold members in the case of mold members of one size, on substitution of the hanger members for another size of mold member the mold arms will no longer be so optimally positioned. This can allow for springing of the molds and the formation of seams on the container being made.